Search PubMed⌕ Search

Biomedical subjects

D E Ward

Publications and source records attributed to D E Ward.

At least 91 records · Page 5Linked to original sources
PubMed1992

Transtelephonic interrogation of the implantable cardioverter defibrillator.

Third generation implantable cardioverter defibrillators (ICDs) have extensive memory capability to store data about the patient's arrhythmias and the effect of therapies delivered by the ICD. However, this data has so far been accessible only when the patient attends the pacing clinic. Two Medtronic 9421 PCD TeletraceR transmitters have been used to interrogate Medtronic 7216A and 7217B PCD S at distances of up to 300 miles from our hospital and transmit the data to a 9420 PCD TeletraceR receiver. Successful transmission of data has been obtained on 50 occasions with 100% data concordance with repeat transmission. The system can reduce the number of unscheduled clinic visits, reduce delay in making a diagnosis following unexpected delivery of a shock therapy, and reassure patients about to be discharged following ICD implantation. The benefits are magnified where patients reside far away from the implanting center.

Electric Countershock↗
PubMed1992

Catheter ablation by low energy DC shocks for successful management of atrial flutter.

OBJECTIVE: To assess the effects of low energy ablation of the substrate for atrial flutter. DESIGN: Initial retrospective analysis of patients undergoing low energy ablation of the atrioventricular node for refractory atrial flutter (group 1) was followed by a prospective assessment of low energy ablation in the posterio-inferior right atrium for the same condition (group 2). SETTING: Tertiary referral centre for management of cardiac arrhythmias. PATIENTS: Seven men (aged 50-67 years) with refractory atrial flutter. INTERVENTIONS: Multiple (3-10) low energy DC shocks with a cumulative energy of 100-245 J in the region of the atrioventricular node in group 1 and 12-15 low energy DC shocks (cumulative energy 110-235 J) guided by the anatomical landmarks of the triangle of Koch and applied directly to the atrial wall. MAIN OUTCOME MEASURE: Freedom from recurrence of atrial flutter. RESULTS: In group 1 despite initial complete atrioventricular block in three patients, atrioventricular conduction had resumed in all by one month. All four, however, were in sinus rhythm at follow up six to 13 months later. Two of the three patients in group 2 were free of atrial flutter at follow up three to four months after ablation. CONCLUSION: Ablation of the atrial flutter substrate with low energy DC shocks is feasible. Precise electrophysiological mapping is not necessary.

Aged↗
PubMed1992

Prognostic value of baroreflex sensitivity testing after acute myocardial infarction.

BACKGROUND: Disturbances of autonomic function are recognised in both the acute and convalescent phases of myocardial infarction. Recent studies have suggested that disordered autonomic function, particularly the loss of protective vagal reflexes, is associated with an increased incidence of arrhythmic deaths. The purpose of this study was to compare the value of differing prognostic indicators with measures of autonomic function and to assess the safety of arterial baroreflex testing early after infarction. METHODS: As part of a prospective trial of risk stratification in post-infarction patients arterial baroreflex sensitivity, heart rate variability, long term electrocardiographic recordings, exercise stress testing, and ejection fraction were recorded between days 7 and 10 in 122 patients with acute myocardial infarction. RESULTS: During a one year follow up period there were 10 arrhythmic events. Baroreflex sensitivity was appreciably reduced in these patients suffering arrhythmic events (1.73 SD (1.49) v 7.83 (4.5) ms/mm hg, 95% confidence interval (CI) 4.8 to 7.3, p = 0.0001). Significant correlations were noted with age (r = -0.68, p less than 0.001) but not left ventricular function. When baroreflex sensitivity was adjusted for the effects of age and ventricular function baroreflex sensitivity was still considerably reduced in the arrhythmic group (2.1 v 7.57 ms/mm Hg, p less than 0.0001). Depressed baroreflex sensitivity carried the highest relative risk for arrhythmic events (23.1, 95% CI 7.7 to 69.2) and was superior to other prognostic variables including left ventricular function (10.4, 95% CI 3.3 to 32.6) and heart rate variability (10.1, 95% CI 5.6 to 18.1). No major complications were noted with baroreflex testing and in particular no patients developed ischaemic or arrhythmic symptoms during the procedure. CONCLUSIONS: Disordered autonomic function as measured by depressed baroreflex sensitivity or reduced heart rate variability was associated with an increase incidence of arrhythmic events in post-infarction patients. Baroreflex testing can be safely performed in the immediate post-infarction period.

Adult↗
PubMed1992

Comparative electrophysiological effects of captopril or hydralazine combined with nitrate in patients with left ventricular dysfunction and inducible ventricular tachycardia.

OBJECTIVE: To assess the electrophysiological and antiarrhythmic effects of pharmacological load manipulation by an angiotensin converting enzyme (ACE) inhibitor (captopril) and a direct vasodilator (hydralazine plus isosorbide mononitrate) in patients with inducible ventricular tachycardia and impaired left ventricular function. DESIGN: Randomised open label cross-over comparison of three regimens. SETTING: Tertiary arrhythmia referral centre. SUBJECTS: Eight patients with reduced left ventricular function and sustained ventricular tachycardia inducible by programmed stimulation. INTERVENTIONS: Three treatment regimens each of 48 hours duration: captopril, hydralazine plus isosorbide mononitrate, and control (no vasodilator). MAIN OUTCOME MEASURES: Changes in central haemodynamics, electrophysiological parameters, and induction of ventricular tachycardia during treatment with captopril, or hydralazine combined with nitrate, compared with a control period. RESULTS: Both vasodilator treatments produced similar balanced reductions in peak systolic pressures and filling pressures compared with controls. Captopril had no effect on sinus cycle length, atrial refractoriness, or intraventricular conduction, but prolonged ventricular effective and functional refractory periods and QT interval during constant rate atrial pacing. Hydralazine combined with nitrate did not significantly alter any electrophysiological variable. Ventricular tachycardia was similarly inducible during all three periods. CONCLUSIONS: Load manipulation by captopril but not hydralazine combined with nitrate prolonged ventricular refractoriness and repolarisation, possibly reflecting a combination of mechano-electrical effect with the restraining influence of ACE inhibitors on reflex sympathetic stimulation.

Aged↗
PubMed1992

Efficacy of flecainide, sotalol, and verapamil in the treatment of right ventricular tachycardia in patients without overt cardiac abnormality.

OBJECTIVE: A comparison of the efficacy of verapamil, sotalol, and flecainide to suppress right ventricular tachycardia (VT) in patients with a clinically normal heart. DESIGN: Patients underwent treatment serially with verapamil (360 mg daily), sotalol (240 or 320 mg daily), and flecainide (200 or 300 mg daily), (the larger dose was for patients heavier than 80 kg) to suppress tachycardia. Each drug was given orally for five half lives before testing. PATIENTS: 23 patients with right VT associated with a clinically normal heart were studied. OUTCOME MEASURES: The effects of drug treatment were examined by the number of ventricular events on 24 hour Holter monitoring, and the ability of tachycardia to be induced by treadmill exercise testing (Bruce protocol) and programmed ventricular stimulation (Wellens protocol), compared with drug free baseline tests. SETTING: Patients were studied in a tertiary referral centre. RESULTS: All three drugs suppressed ventricular salvos (> 3, < 5 consecutive ventricular premature contractions) (p < 0.01) and VT (p < 0.05) on Holter monitoring and did not differ statistically in effect. Exercise induced VT was also suppressed by all three drugs (p < 0.01), and of these sotalol was the most effective although this was not statistically significant (14/23 inducible when drug free, 4/23 on flecainide, 2/23 on sotalol, 5/23 on verapamil). Sustained and non-sustained VT induced by programmed stimulation was also suppressed by the three drugs (p < 0.01) and again sotalol was the best of these though the differences did not achieve statistical significance (17/23 inducible when drug free, 4/17 on flecainide, 2/17 on sotalol, and 6/17 on verapamil). Proarrhythmic effects of drugs were found in a few patients. There was no difference in the efficacy of the drugs in patients with histological abnormalities of the myocardium when compared with those of normal histology. CONCLUSIONS: Ventricular tachycardia associated with a clinically normal heart can be suppressed by flecainide, sotalol, or verapamil. In individual patients sotalol was the most frequently effective drug (effective in > 89% of patients) and is a suitable choice for first line treatment.

Adult↗
PubMed1992

Intravascular ultrasound imaging of the coronary arteries: an in vitro evaluation of measurement of area of the lumen and atheroma characterisation.

OBJECTIVE: To assess the accuracy of measurement of area of the lumen, and sensitivity, and specificity of detection of atheroma in coronary arteries in vitro with a commercially available 20 MHz intravascular ultrasound system. SETTING: A teaching hospital department of cardiology with the support of the department of cardiovascular pathology. PROCEDURE: 10 segments of coronary artery were removed from cadaver hearts. Intravascular ultrasound imaging was performed at fixed levels and the vessels were then sectioned and photographed before histological preparation. An independent blinded observer measured luminal area and assessed the presence of atheroma on the intravascular ultrasound images of 76 vessel sections (304 quadrants). The sensitivity and specificity of detection of atheroma was assessed in comparison with the histologically prepared sections. Luminal areas from intravascular ultrasound, photographs of cross sections of the vessels and histological sections were compared with the technique of limits of agreement. RESULTS: Overall 36% of the 304 quadrants studied histologically had identifiable atheroma. Intravascular ultrasound sensitivity for atheroma was 0.593 and the specificity was 0.839. The positive predictive value was 0.674, and the relative risk 3.139. Values for area of the vessel lumen were on average 9.4 mm2 (confidence interval (CI) 8.6-10.2 mm2) larger than those measured from photographs and 10.7 (CI 9.8-11.6 mm2) larger than those measured from the histological sections. CONCLUSIONS: The intravascular ultrasound system assessed in this study significantly overestimated coronary vessel luminal area and had low sensitivity and specificity for detection of atheroma. Improvements in image resolution are required before this system can provide useful information on coronary artery size and morphology.

Coronary Artery Disease↗
PubMed1991

Risk stratification for arrhythmic events in postinfarction patients based on heart rate variability, ambulatory electrocardiographic variables and the signal-averaged electrocardiogram.

The value of heart rate variability, ambulatory electrocardiographic (ECG) variables and the signal-averaged ECG in the prediction of arrhythmic events (sudden death or life-threatening ventricular arrhythmias) was assessed before hospital discharge in 416 consecutive survivors of acute myocardial infarction. During the follow-up period (range 1 to 1,112 days), there were 24 arrhythmic events and 47 deaths. The initial relation between several prognostic factors and arrhythmic events was explored with use of the Kaplan-Meier product limit estimates of survival function. Impaired heart rate variability less than 20 ms (p less than 0.0000), late potentials (p less than 0.0000), ventricular ectopic beat frequency (p less than 0.0000), repetitive ventricular forms (p less than 0.0000), left ventricular ejection fraction less than 40% (p less than 0.02) and Killip class (p less than 0.02) were identified as significant univariate predictors of arrhythmic events. When these variables were analyzed by using a stepwise Cox regression model, only impaired heart rate variability, followed by late potentials and repetitive ventricular forms remained independent predictors of arrhythmic events. The combination of impaired heart rate variability and late potentials had a sensitivity of 58%, a positive predictive accuracy of 33% and a relative risk of 18.5 for arrhythmic events and was superior to other combinations including those incorporating left ventricular function, exercise ECG, ventricular ectopic beat frequency and repetitive ventricular forms. These results suggest that a simple method of assessment based on heart rate variability and the signal-averaged ECG can select a small subgroup of survivors of myocardial infarction at high risk of future life-threatening arrhythmias and sudden death.

Arrhythmias, Cardiac↗
PubMed1991

The electrophysiological effects of flosequinan.

We have evaluated the acute electrophysiological effects of flosequinan in 18 patients with normal ventricular function. Following intravenous infusion of flosequinan 100 mg over 1 h, mean (SD) systolic blood pressure fell from 131 +/- 19 to 120 +/- 22 mmHg (P less than 0.02) and there was significant shortening of sinus cycle length (732 +/- 151 to 575 +/- 93 ms, P less than 0.001), AH interval (110 +/- 45 to 71 +/- 19 ms, P less than 0.01), QRS duration (98 +/- 28 to 91 +/- 26 ms, P less than 0.02) and QT interval (373 +/- 47 to 337 +/- 35 ms, P less than 0.001), but no change in sinus node recovery time, intra-atrial conduction time, HV interval or the corrected QTc interval. There was a reduction in both anterograde atrioventricular Wenckebach cycle length (299 +/- 53 to 259 +/- 52 ms, P less than 0.01) and retrograde ventriculoatrial Wenckebach cycle length (375 +/- 77 to 300 +/- 56 ms, P less than 0.01). There was no change in atrial or ventricular effective refractory period (ERP) but atrial functional refractory period (FRP) shortened (233 +/- 31 to 212 +/- 24 ms, P = 0.07) as did ventricular FRP (249 +/- 24 to 234 +/- 21 ms, P less than 0.01). Patients received an oral dose of flosequinan 50 mg 12 h later. By 24 h, sinus cycle length, QRS duration and the QT interval had all returned towards baseline values, but ventricular ERP had lengthened (199 +/- 22 to 215 +/- 26 ms, P less than 0.06).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Signal averaging of the electrocardiogram in the remote differential diagnosis of broad complex tachycardias.

The diagnosis of the origin of a broad complex tachycardia may be difficult, especially in the absence of a 12-lead electrocardiogram of the tachycardia. This study investigates the value of signal averaging in the differential diagnosis of broad complex tachycardia. Signal averaging during sinus rhythm was performed in 102 consecutive patients who presented with broad complex tachycardia (QRS width greater than 110 ms), in whom a definitive electrophysiological diagnosis was made. The presence of late potentials was determined on the basis of two definitions, the second including total QRS duration. The patients studied included 75 with ventricular tachycardia; 33 of these patients had suffered previous myocardial infarction, five had dilated cardiomyopathy, and 37 had a 'normal' heart. Of the 27 patients with supraventricular tachycardia, 22 had an atrioventricular accessory pathway (seven with a delta wave in sinus rhythm), three had atrioventricular nodal tachycardia and two had atrial tachycardia. The sensitivity of late potentials for the diagnosis of ventricular tachycardia was low utilizing both definitions (28% and 45%) although specificity was high (96% and 95%). The sensitivity for the diagnosis of ventricular tachycardia was higher for patients with ischaemic heart disease (43% and 70%) but very low for patients with ventricular tachycardia and a normal heart (16% and 22%). In conclusion, signal averaging in the remote diagnosis of broad complex tachycardia is specific but not sensitive for ventricular tachycardia, which limits its usefulness in selecting patients for electrophysiological study.

Coronary Disease↗
PubMed1991

Transcoronary atrioventricular nodal modification using microvascular collagen.

Surgical and catheter based techniques for atrioventricular (AV) nodal modification have recently been described. Similarly, transcoronary embolization for the treatment of arrhythmias has recently emerged as a potentially useful approach. This report reviews our experience of a novel technique using embolization of the AV node with an inert agent, cross-linked collagen, for the treatment of AV nodal reentrant tachycardia. Three patients with refractory nodal tachycardia received 0.1-0.5 mL cross-linked collagen (2 mg/mL) delivered via a catheter placed within the nodal artery. All developed transient complete AV block with subsequent recovery of conduction. Two patients have had no further tachycardia and were noninducible at restudy. One patient required electrical modification because of recurrent symptoms. One patient sustained a limited posterior infarct due to back-spill of collagen into the distal right coronary artery. This novel technique provides an alternative approach to a cure for AV nodal tachycardia without producing long-term heart block.

Atrioventricular Node↗
PubMed1991

RR variability and baroreflex sensitivity in patients with ventricular tachycardia associated with normal heart and patients with ischemic heart disease.

Recent studies have suggested that disordered autonomic function, particularly the loss of protective vagal reflexes are associated with an increased incidence of arrhythmic deaths following myocardial infarction (MI). Heart rate variability (HRV) and baroreflex sensitivity (BRS) are measures of myocardial autonomic function and predict arrhythmic deaths post-MI. Patients with ventricular tachycardia associated with a "normal heart" frequently have exercise-induced arrhythmia suggesting that the autonomic nervous system is important in the genesis of this form of ventricular tachycardia (VT). This study examines HRV and BRS in patients with VT associated with a "normal heart" and compares these values to patients post-MI with and without evidence of arrhythmia. Twenty patients with VT associated with a "normal heart," 16 patients with MI but without arrhythmia on follow-up, and 11 patients with MI and VT on follow-up were studied. HRV was measured from 24-hour Holter recordings and BRS was measured from plots of change in systolic blood pressure versus change in heart rate following an intravenous injection of 0.4-0.6 mg phenylephrine. HRV was significantly higher in the patients with VT associated with a normal heart (34.2 +/- 10.8 msec) compared to the patients post-MI, without (23.7 +/- 6.7 msec) and with (14.8 +/- 3.8 msec) arrhythmia (F = 9.2, P less than 0.001) and these differences were unaffected by adjustment for age.(ABSTRACT TRUNCATED AT 250 WORDS)

Autonomic Nervous System↗
PubMed1991

A comparison of intravenous propafenone and flecainide in the treatment of tachycardias associated with the Wolff-Parkinson-White syndrome.

UNLABELLED: We compared the electrophysiological effects of intravenous propafenone and flecainide on accessory pathway conduction by a randomized crossover study in 16 patients with Wolff-Parkinson-White syndrome. The antegrade refractory period of the pathway increased from 256 +/- 18 msec at baseline to 288 +/- 13 msec on propafenone (P less than 0.05) and to 296 +/- 27 msec on flecainide (P = 0.075). The minimum preexcited RR interval during atrial fibrillation or incremental atrial pacing was prolonged from 225 +/- 37 msec to 262 +/- 22 msec by propafenone (P less than 0.05) and to 301 +/- 31 msec by flecainide (P less than 0.005). The prolongation was significantly greater with flecainide than propafenone (P less than 0.05). Both drugs increased tachycardia cycle length (TCL) from 310 +/- 35 msec to 354 +/- 37 msec (propafenone P less than 0.005) and to 352 +/- 37 msec (flecainide P less than 0.01). Both propafenone and flecainide blocked antegrade conduction in the pathway in five patients. Both drugs rendered atrial fibrillation noninducible in seven patients and orthodromic tachycardia noninducible in five patients. CONCLUSIONS: (1) Flecainide causes a greater prolongation of minimum preexcited RR interval than propafenone; (2) There is no significant difference between propafenone and flecainide on the inducibility of arrhythmias, TCL, or incidence of antegrade conduction block.

Adult↗
PubMed1991

The effect of age on the electrophysiological and autonomic correlates of sudden death after acute myocardial infarction.

To examine the influence of age on the autonomic and electrophysiological correlates of sudden death after myocardial infarction, 223 patients aged less than 60 and 195 patients aged greater than or equal to 60 were followed up for a mena of 790 days. The patients had Holter monitoring and a signal-averaged ECG 5-11 days after infarction. A mean ventricular ectopic beat frequency greater than 10 beats/hour (VE10) was present in 17.0% of young versus 28.2% of old patients (P less than 0.01); a low heart heart variability index in 17.9% of young but in 32.3% of old patients (P less than 0.001) and late potentials in 17.5% but 32% of young and old patients, respectively (P less than 0.01). There was no difference in the incidence of sudden death between young and old patients (3.6% vs 3.1%). However, sudden death accounted for 50%, compared with 24% of all deaths in the young and old groups, respectively (P less than 0.01). Sudden death was more closely associated with low heart rate variability and VE10 in the young than in the older group. The predictive values of a heart rate variability index less than 20 units with VE10 in younger patients were a sensitivity of 50%, a positive predictive accuracy (PPA) of 33% and risk ratio (RR) of 18 (P less than 0.001); these values did not reach significance in older patients (16.7%, 4.3% and 1.4%, respectively.)(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1991

Automatic recognition of ventricular arrhythmias using temporal electrogram analysis.

Future antitachycardia devices must be able to deliver a variety of therapies according to the requirements of the underlying arrhythmia. To ensure that appropriate treatment is prescribed the device must use a detection algorithm that is able to discriminate between multiple arrhythmias. Current criteria such as rate, change of rate, duration at high rate, and high rate stability are inadequate for this purpose. Many algorithms that evaluate the morphology of the endocardial electrogram are of too great a complexity to be incorporated in implantable devices that require real-time analysis without undue power consumption. In this study the sensitivity of a simple morphological technique (temporal electrogram analysis) is examined. The method sets threshold 'rails' above and below the isoelectric line and classifies ECG complexes according to the sequence and duration of rail excursions. A total of 27 ventricular tachyarrhythmias were induced in 25 patients (17 with a history of recurrent arrhythmias and eight undergoing risk stratification postmyocardial infarction). Temporal electrogram analysis (TEA), initially detected the onset of the ventricular arrhythmia in all patients whose surface ECG showed polymorphic or right bundle branch block pattern tachycardia, in 5/8 of cases with left bundle branch block pattern and in 4/5 of patients with concordant complexes across the precordial leads. After minor modifications the overall sensitivity of the method was improved to 95% (26/27 arrhythmias detected). TEA is a technique of low computational demands, which in this study, reliably discriminated between resting sinus rhythm and ventricular arrhythmias.

Adult↗
PubMed1991

The right ventricular outflow tract as an alternative permanent pacing site: long-term follow-up.

The long-term characteristics of the right ventricular outflow tract have been assessed as an alternative permanent pacing site to the right ventricular apex. Thirty-three consecutive patients requiring ventricular pacing were randomized to be paced from one of the two sites. Pacing was performed using a screw-in lead, and a programmable pacemaker was used to facilitate threshold testing. There was no significant difference in the lead positioning time or any acute implant measurement (e.g., threshold at 0.5 msec 0.4 +/- 0.2 V for both sites, P = 0.99). Chronic measurements were also comparable during follow-up (mean 73 months) with a mean threshold at most recent follow-up of 0.15 +/- 0.2 msec (apex) and 0.13 +/- 0.21 msec (outflow tract) at 5 V, P = 0.81. There was only one pacing related complication, a lead dislodgment (outflow tract) in a pacemaker twiddler. Overall, both sites were highly satisfactory.

Aged↗